Nuclear Physics Quiz

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Questions and Answers

In the equation $ abla E = E_i - E_f = hƒ$, what does 'h' represent?

The frequency of emitted radiation.

Planck's constant. (correct)

The energy of the atom.

The mass number of the nucleus.

What is true about the mass number A in terms of nucleons?

A is the number of electrons in the atom.

A is the sum of protons and neutrons in the nucleus. (correct)

A only includes protons.

A equals the charge number.

Which of the following elements does not contain a neutron?

Carbon

Oxygen

Helium

Hydrogen (correct)

Which of the following particles can be found in the nucleus of an atom?

Protons and neutrons Signup and view all the answers

What does the term nucleon refer to?

Either a proton or a neutron. Signup and view all the answers

What charge do neutrons carry?

No charge. Signup and view all the answers

Which of the following best describes the size and shape of most nuclei?

Approximately spherical. Signup and view all the answers

Which particle is emitted as a positron?

Beta particle Signup and view all the answers

What is the primary reason Marie Curie is renowned in scientific history?

Her work on radioactivity Signup and view all the answers

How do alpha particles interact in a magnetic field?

They are deflected upward Signup and view all the answers

What does the decay constant ( λ) indicate in radioactivity?

The probability of decay per nucleus per second Signup and view all the answers

Which of the following statements is true about gamma rays?

They are high-energy photons Signup and view all the answers

What is the approximate penetrating ability of beta particles?

They can penetrate a few mm of aluminum Signup and view all the answers

Who was the pioneering scientist that discovered radioactivity?

Henri Becquerel Signup and view all the answers

Which of the following is a characteristic of heavy radioactive nuclei?

They undergo disintegration due to instability Signup and view all the answers

What significant contribution did Joseph John Thomson make to physics?

Discovered the electron. Signup and view all the answers

Which model of the atom describes electrons as being embedded in a volume of positive charge?

Thomson's Model Signup and view all the answers

According to Rutherford's model, where is the positive charge concentrated?

In the atom's nucleus Signup and view all the answers

What does Bohr's model state about certain electron orbits?

Only specific orbits, called stationary states, are stable. Signup and view all the answers

What phenomenon occurs when an electron transitions from a higher-energy stationary state to a lower-energy one?

Emission of electromagnetic radiation Signup and view all the answers

In Bohr's model, what prevents the electron from spiraling into the nucleus?

Only certain orbits are allowed and stable. Signup and view all the answers

Who headed the Institute for Advanced Studies in Copenhagen and contributed to quantum mechanics?

Niels Bohr Signup and view all the answers

What is the decay rate R of a sample defined as?

The number of decays per second Signup and view all the answers

Which of the following correctly describes the half-life of a radioactive material?

The time required for half of the undecayed nuclei to decay Signup and view all the answers

Which process involves a large nucleus splitting into two smaller nuclei?

Fission Signup and view all the answers

Why are neutrons effective in penetrating atomic nuclei?

They are neutral particles, not interacting electrically. Signup and view all the answers

Which materials are considered good moderators for fast neutrons?

Paraffin and water Signup and view all the answers

What type of radiation damage primarily affects reproductive cells?

Genetic damage Signup and view all the answers

What is the primary damage mechanism caused by radiation in biological organisms?

Damage to DNA in the cell's nucleus Signup and view all the answers

Which type of radiation can penetrate deeper and cause significant damage due to its lack of interaction with materials?

Neutrons Signup and view all the answers

What aspect of radiation determines the degree and type of radiation damage experienced?

Type and energy of the radiation Signup and view all the answers

How is one rad quantitatively defined in terms of energy absorption?

Energy increase of 1 kg of biological tissue by 1 x 10-2 J Signup and view all the answers

Which radiation type is known for causing extensive damage but has low penetrating power?

Alpha particles Signup and view all the answers

What does the Relative Biological Effectiveness (RBE) measure?

Biological damage produced by a specific radiation compared to standard x-radiation Signup and view all the answers

What form of radiation damage can result from high levels of radiation exposure to somatic cells?

Increased risk of cancer Signup and view all the answers

What does the rem measure in radiation exposure?

The biological effect of radiation on humans Signup and view all the answers

What is the recommended upper limit of radiation exposure for the general population excluding background radiation?

0.50 rem/yr Signup and view all the answers

Which method utilizes neutron activation analysis in its application?

Tracing chemicals in reactions Signup and view all the answers

What is the primary risk factor associated with occupational radiation exposure?

Ingestion or inhalation Signup and view all the answers

Who is credited with the accidental discovery of X-rays?

Wilhelm Conrad Röntgen Signup and view all the answers

Which of these factors is crucial for the effectiveness of radiation therapy?

The rapid division of cells Signup and view all the answers

What unit has replaced the rem in measuring radiation dosages?

The gray (Gy) Signup and view all the answers

Which statement regarding background radiation is accurate?

It contributes to about 0.13 rem/yr of exposure Signup and view all the answers

What is the significance of Bohr’s stationary states in his model of the atom?

They prevent electrons from emitting energy while in motion. Signup and view all the answers

How did Rutherford's model of the atom differ from Thomson's model?

Rutherford’s model concentrated positive charge in a nucleus. Signup and view all the answers

What does Bohr's model predict when an electron transitions from a higher-energy stationary state?

The atom emits energy in the form of electromagnetic radiation. Signup and view all the answers

Which of the following would NOT be an implication of Thomson's model of the atom?

Nuclear forces hold electrons in specific orbits. Signup and view all the answers

What aspect of Niels Bohr’s contributions to atomic physics is primarily recognized?

Establishing that stable electron orbits are determined by quantum numbers. Signup and view all the answers

What is the primary characteristic of the neutron that complicates its detection?

It has no charge. Signup and view all the answers

What does the formula $A=Z+N$ represent in nuclear physics?

The sum of protons and neutrons in a nucleus. Signup and view all the answers

Which of the following best describes Planck's constant used in quantum mechanics?

A universal constant related to energy and frequency. Signup and view all the answers

What significant observation was made from Rutherford's scattering experiments?

Most atomic mass is located in the nucleus. Signup and view all the answers

When a photon is absorbed by an electron, what happens to the electron's energy state?

It transitions to a higher energy level. Signup and view all the answers

What is the primary reason that nuclei are stable despite the repulsive forces between protons?

The nuclear attractive force Signup and view all the answers

Which of the following statements about the density of nuclei is correct?

All nuclei have nearly the same density regardless of size Signup and view all the answers

What does binding energy represent in the context of nuclei?

Energy released when a nucleus forms from separate nucleons Signup and view all the answers

When does the attraction of the nuclear force become ineffective between nucleons?

When separation exceeds several fermis Signup and view all the answers

Which situation describes the stability of heavy nuclei?

Heavy nuclei need more neutrons than protons for stability Signup and view all the answers

Study Notes

Basics of Nuclear Physics

Reference material: "Physics for Scientists and Engineers with Modern Physics" by Raymond A. Serway and John W. Jewett, Jr., 10th edition, 2019, Chapters 41 and 43
Course: BME 229, Fall 2024

Joseph John Thomson (1856-1940)

English physicist
Received Nobel Prize in 1906
Considered the discoverer of the electron
Worked with cathode ray deflection in electric fields
Pioneered the field of subatomic particles

Early Models of the Atom - Thomson's

J.J. Thomson determined the charge-to-mass ratio of electrons
Atomic model: a volume of positive charge with electrons embedded throughout
Atom is electrically neutral overall

Early Models of the Atom - Rutherford's

Rutherford's planetary model, based on thin foil experiments
Positive charge concentrated in a small, dense nucleus
Electrons orbit the nucleus

Niels Bohr (1885-1962)

Danish physicist
Early participant in the development of quantum mechanics
Headed the Institute for Advanced Studies in Copenhagen
Awarded 1922 Nobel Prize in physics for his work on the structure of atoms and the radiation emanating from them

Bohr's Model of the Atom, Part 1

Electrons orbit the nucleus in circular paths
Coulomb force provides the centripetal acceleration
Orbits have specific, discrete radii

Coulomb's Law

The electrostatic force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them
SI unit of charge: coulomb (C)
Coulomb constant (kₑ) = 8.9876 x 10⁹ N⋅m²/C² = 1/(4πε₀)

Bohr's Model of the Atom, Part 2

Bohr's stationary states: electron orbits are stable without emitting radiation while accelerating
Atom's energy remains constant in these orbits
Classical mechanics can describe the electron's motion in these stable orbits

Bohr's Model of the Atom, Part 3

Radiation emitted when electron transitions from a higher energy level to a lower one
Frequencies of emitted radiation are related to changes in the atom's energy
Frequencies are independent of the electron's orbital motion

Milestones in the Development of Nuclear Physics

1896: Becquerel discovered radioactivity in uranium compounds
Rutherford identified three main types of radioactivity: alpha (He nuclei), beta (electrons), and gamma (high-energy photons)
1911: Rutherford, Geiger, and Marsden performed scattering experiments that demonstrated the nucleus's concentrated positive charge and small size.

Some Properties of Nuclei

Nuclei are composed of protons and neutrons
Atomic number (Z): number of protons in the nucleus; also called charge number
Neutron number (N): number of neutrons in the nucleus
Mass number (A): total number of nucleons (protons + neutrons) in the nucleus
Nucleon: a generic term for a proton or neutron

Symbolism

Nuclide: specific combination of atomic number (Z) and mass number (A) that represents a nucleus.
X represents the chemical symbol of the element

More Properties

All atoms of a given element have the same number of protons. However, they can have varying numbers of neutrons
Isotopes: atoms of the same element with different numbers of neutrons (same Z, but different N and A values)
Isotopes may have different natural abundances

Charge

Proton: +e charge
Electron: -e charge (e = 1.6 x 10⁻¹⁹ C)
Neutron: no charge

Mass

Atomic mass units (u) are used to express masses.
1 u = 1.660539 x 10⁻²⁷ kg
Mass of one atom of ¹²C is exactly 12 u.
Mass can also be expressed in MeV/c²

Some Masses in Various Units

Table of masses for particles in kg, amu, and MeV/c²

Prefixes

Table listing prefixes for powers of 10

Size of the Nucleus - Continued

Radius calculation based on closest approach of an alpha particle to the nucleus. Results in a very small size for the nucleus
Typical units: femtometers (fm) = 10⁻¹⁵ m

Size of the Nucleus - Final

Nuclei are approximately spherical
Average radius (r) is proportional to the cube root of the mass number (A): r α A¹/³

Density of Nuclei

Volume of a nucleus is proportional to the total number of nucleons
Nuclei have nearly identical densities
Nucleons densely packed

Nuclear Stability

The nucleus is stable due to the strong, short-range nuclear attraction force between all nuclear particles. This force is stronger than the Coulomb repulsion force at short ranges
Stability differs for light vs. heavy nuclei.

Features of the Nuclear Force

Attractive force acting between all nuclear particles
Extremely short range, typically less than a few fermis.
Force is independent of charge.

Nuclear Stability Cont.

Light nuclei are most stable when the number of neutrons (N) equals the number of protons (Z)
Heavy nuclei are most stable when N > Z.
Nuclei become unstable for Z > 83

Binding Energy

Binding energy: the difference in energy between the bound system and the separated nucleons in a nucleus.
Energy released when combining nucleons to form a nucleus (energy of the system is lowered)
Calculated using conservation of energy and the mass-energy equivalence principle (E = mc²)

Marie Curie (1867-1934)

Polish scientist
Shared Nobel Prize in Physics in 1903 with Pierre Curie and Becquerel for studies of radioactivity
Won Nobel Prize in Chemistry in 1911 for discoveries of radium and polonium
Family of Nobel Prize winners

Radioactivity

Spontaneous emission of radiation from an unstable nucleus

Radioactivity - Types of Decay

Three types of radioactivity: α (alpha particles - He nuclei), β (beta particles - electrons or positrons), γ (gamma rays - high-energy photons)

Distinguishing Types of Radiation

Charged particles deflected in opposite directions by a magnetic field
Gamma rays not deflected due to no charge
Alpha particles deflected upward; Beta particles deflected downward.

Penetrating Ability of Particles

Alpha particles: low penetrating power (stopped by paper)
Beta particles: moderate penetrating power (stopped by aluminum)
Gamma rays: high penetrating power (stopped by lead or significant material)

Terminology Notes

"Radiation" is a historical term that encompasses all emissions from radioactive nuclei, not explicitly limited to electromagnetic radiation
Alpha and beta emissions are particles with nonzero rest mass/kinetic energy, not just electromagnetic waves

The Decay Constant

Decay rate proportional to the number of particles in a sample
Defined by the decay constant (λ), representing the decay probability per nucleus per second.

Decay Rate

Decay rate (R) is the number of decays per second.
The decay rate at time t = 0 is R₀.
A measure of the activity of a radioactive sample

Decay Curve and Half-Life

Decay curve follows an exponential equation
Half-life (T₁/₂): the time interval where half of the nuclei in a sample decay

Half-life - Continued

During each half-life, the number of undecayed nuclei decreases by half

Units

Curie (Ci): older unit for radioactivity (3.7 x 10¹⁰ decays/second)
Becquerel (Bq): SI unit for radioactivity (1 decay/second)
Other units include millicurie and microcurie

Applications of Nuclear Physics

Processes of Nuclear Energy Generation

Fission: heavy nucleus splits into lighter nuclei
Fusion: light nuclei combine into a heavier nucleus

Interactions Involving Neutrons

Neutrons are not affected by Coulomb forces
They can easily penetrate matter and interact with nuclei

Fast Neutrons

High energy neutrons capable of penetrating deep into materials
Moderators (materials like paraffin or water) are used to slow down neutrons through elastic collisions.

Fission Example: ²³⁵U

Neutron-induced fission of ²³⁵U (Uranium-235) producing Barium (Ba) and Krypton (Kr), releasing neutrons

Chain Reaction

Fission releases neutrons that can cause more fissions, creating a chain reaction
Can be controlled or uncontrolled

Chain Reaction - Diagram

Chain reaction example showing the cascading effect of neutron-induced fission

Nuclear Fusion

Two light nuclei combine to form a heavier nucleus
Mass of the final nucleus is less than the sum of the initial nuclei
Energy released according to E = Δmc²

Fusion in the Sun

Fusion reactions power stars like the sun
High temperature needed for fusion reaction to occur

Advantages of a Fusion Reactor

Inexpensive fuel source (water)
Few radioactive byproducts produced

Deuterium

A stable isotope of hydrogen, used in fusion reactions as a fuel

Radiation Damage

Radiation absorbed by matter can cause damage, depending on type and energy of radiation and the properties of the matter

Radiation Damage, continued

Neutron bombardment: weakens metals
Biological damage: primary damage to the DNA in cells (ionization effects)

Types of Radiation Damage in Cells

Somatic damage: affects non-reproductive cells, cancer possibility with high radiation
Genetic damage: affects reproductive cells, defective offspring
DNA damage is the primary cause of cell damage

Damage Dependence on Penetration

Units of Radiation Exposure

Roentgen (R): amount of ionizing radiation that produces a specific electrical charge in air.
Rad: unit of radiation absorbed dose

More Units

RBE (Relative Biological Effectiveness): accounts for varying effects of different radiation types, such as alpha particles, beta particles, neutron and gamma rays.
Rem: radiation equivalent in man - RBE multiplier for the absorbed dose of radiation.

RBE Factors, A Sample

Table of RBE factors for different types of ionizing radiations

Radiation Levels

Background radiation: natural radiation from sources like rocks, soil, and cosmic rays.
Occupational limits: exposure limits for workers in radiation-related industries.
Exposure units for radiation: 0.13 rem/year and 0.5 rem/year.

Radiation Levels - Continued

50% mortality rate at 400-500 rem of exposure.
Gray (Gy): SI unit replacing rad
Sieverts (Sv): SI unit replacing rem

SI Units, Table

Table showing conversion factors between older and newer units for radiation exposure

Other Applications of Radiation

Tracing: using radioactive materials to track chemicals in processes
Materials analysis: neutron activation analysis using nuclear reactions
Radiation therapy: cancer treatment using ionizing radiation

Other Applications of Radiation - Continued

Food Preservation: using high levels of radiation to eliminate bacteria and mold

Medical Nuclear Physics

X-ray, gamma ray, neutron, electron beam use for medical diagnostics and treatments
Evaluation of equipment, calibration and safety aspects of ionizing radiations

Discovery of X-rays

Wilhelm Conrad Röntgen's accidental discovery in 1895.
Images of biological materials obtained.

Gamma Camera Scan

Medical imaging technique using radioactive tracers
Detects areas of increased blood flow, metabolism, or inflammation
Uses Technetium-99m (⁹⁹mTc) as a common tracer

Cell Killing By Ionizing Radiation

Microscopic damage to chromosomes as a result of ionizing radiation.

Radiation Therapy

Modern radiation therapy equipment (LINAC) using high-energy X-rays and electrons

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Description

Test your knowledge on key concepts of nuclear physics. This quiz covers topics such as radiation, decay processes, and the fundamental particles found in an atom's nucleus. Explore the contributions of notable scientists like Marie Curie along with the characteristics of various particles and elements.